Tiling specifies the number of different probes covering a given nucleotide in your submitted target. The default is 1X tiling which involves probes placed end to end with no overlap, ensuring each target nucleotide is covered by 1 probe. At 2X tiling, an overlap would be introduced between probes to ensure each nucleotide is covered by 2 probes. We suggest that you increase tiling for regions difficult to enrich.